The present invention relates to an improved saw tooth for circular saws, and more particularly, to a saw tooth having inserts to provide multiple angled cutting edges.
Saw teeth for circular saws of the type mounted on a feller head for a tree felling apparatus have undergone considerable change in the last few years.
U.S. Pat. No. 4,932,447, Morin, 1990, and U.S. Pat. No. 5,205,199, MacLennan, 1993, represent saw teeth which have become the standards in the industry. Morin ""447 and MacLennan ""199 both teach a replaceable saw tooth with four sides which can be rotated when the active cutting tips and edges become dull or worn. The saw tooth generally has a four-sided main body with a mounting end and a cutting end. The MacLennan patent further provides V-shaped cutting edges at the cutting end, with four planar surfaces defining cutting tips at the apex of these somewhat triangular surfaces. Flat triangular carbide inserts can overlie the flat surfaces to reinforce the cutting edges. These inserts are brazed to the tooth head.
MacLennan et al, in their U.S. Pat. No. 5,644,965, 1997, describe an improved saw tooth having V-shaped cutting edges. The four-sided main body of the saw tooth includes seats for receiving inserts. The inserts which are made of hardened material are provided with cutting tips and cutting edges and are retained against the main body by a clamp nut. Thus, when the edges and tips are worn or damaged from impact, the inserts can be replaced without rotating the tooth. The tooth is rotated only when the seat of the main body is damaged.
The saw tooth, which has fixed or replaceable hardened inserts forming V-shaped cutting edges, provides good cutting performance. However, it should be noted that in those prior art saw teeth, adjacent inserts abut each other, thereby forming weak points at the junction of the respective V-shaped cutting edges. In a worst case scenario, a slight gap may exist between adjacent inserts and, therefore, the V-shaped cutting edges are not actually continuous at those junctions thereof, which will adversely affect the cutting performance of the saw tooth.
In U.S. Pat. No. 5,307,719, issued on May 3, 1994, MacLennan describes a saw tooth similar to those described in U.S. Pat. No. 5,205,199. The improvement of MacLennan ""719 lies in that adjacent insert ends of the hardened inserts overlap at the intersection of the two adjacent surfaces. The overlap of the hardened inserts is provided by forming a V-shaped notch in an end of an edge which is adapted to receive an angled end of an edge of an adjacent hardened insert. However, because it is limited by the thickness and angled position of the hardened inserts, the V-shaped notch only provides very limited space for the overlap. Therefore, such an overlap configuration cannot significantly prevent weakened areas in the cutting end of the tooth.
There is a need for improved configuration of the saw tooth having inserts forming V-shaped cutting edges, to overcome these shortcomings.
It is an object of the present invention to provide a saw tooth having inserts forming angled cutting edges about the periphery of a cutting end of the saw tooth, wherein adjacent inserts are overlapped to provide strengthened cutting edges at the junctions of adjacent inserts.
A construction in accordance with the present invention includes a saw tooth for a circular saw blade wherein the tooth comprises a multi-faceted shaped body having a mounting end, a larger cutting end and a plurality of sides extending between the mounting end and the cutting end. The sides form corners at the cutting end where they meet. A seating surface is provided on the cutting end at each of the corners. Each of the seating surfaces slopes inwardly and is defined between two edges diverging from a corresponding corner. A hardened insert is fastened to each seating surface to form a single cutting tip with a pair of receding cutting edges. Adjacent inserts overlap one another and provide angled cutting edges about the entire periphery of the cutting end. A seat-notch in each of the seating surfaces and an insert-notch in each of the inserts are provided so that the seat-notch and the insert-notch in combination form a groove for receiving a section of an adjacent insert, in order to permit the overlapping of adjacent inserts.
The inserts can either be permanently fastened to the tooth head or can be detachably fastened to the tooth head in order to permit the inserts to be replaceable when they are worn or damaged.
Other advantages and features of the present invention will be better understood with reference to the preferred embodiment described hereinafter.